BANGKOK - Thailand went to the polls under heavy security on Sunday in an election that could push the divided country deeper into political turmoil and leave the winner paralyzed for months by street protests, legal challenges and legislative limbo.

Voting started peacefully a day after seven people were wounded by gunshots and explosions during a clash between supporters and opponents of embattled Prime Minister Yingluck Shinawatra in a north Bangkok stronghold of her Puea Thai Party.

Voting was called off in the district and some other polling stations were unable to open because of pressure by anti-government protesters. Polling outside the capital and the south was unaffected.

"The situation overall is calm and we haven't received any reports of violence this morning," National Security Council chief Paradorn Pattanatabutr told Reuters. "The protesters are rallying peacefully to show their opposition to this election."

The usual campaign billboards, glossy posters and pre-election buzz have been notably absent, as will be millions of voters fearful of violence or bent on rejecting a ballot bound to re-elect the political juggernaut controlled by Yingluck's billionaire brother, Thaksin Shinawatra.

Thaksin, 64, is loved and loathed in Thailand, but his parties have won every poll since 2001. His opponents say he is a corrupt crony capitalist who rules by proxy from self-exile in Dubai.

"We're not blocking the election. We're postponing it," said Nipon Kaewsook, 42, one of the hundreds of protesters blocking Ratchathewi District Office in central Bangkok to prevent the distribution of dozens of ballot boxes.

"We still need an election, but we need reform first," added Nipon, an English teacher from Phattalung in southern Thailand.

Protesters shouted "Yingluck get out!" and "Thaksin go to jail!" They took celebratory selfies in front of the ballot boxes, placed in a car park at the back of the building.

Victory celebrations for Yingluck would probably be muted. With parliamentary seats unable to be filled, she could find herself on shaky ground, exposed to legal attacks and unable to pass bills and budgets crucial to reviving a stuttering economy.

Yingluck last week refused to postpone the election, even though a fifth of those registered for advance voting were unable to cast ballots after protesters blocked polling stations in 49 of 50 Bangkok districts as part of a "shutdown" of key intersections. In 28 southern constituencies, no votes will be cast because no candidates could sign up.

The Election Commission says results will not be available on Sunday. Its commissioners are braced for a deluge of complaints and challenges to the results.

"There's been a lot of obstruction, so much, every single step of the way," commission secretary-general Puchong Nutrawong told Reuters.

"We don't want this election to be a bloody election. We can get every single agency involved to make this election happen, but if there's bloodshed, what's the point?"